There are only 2 or 3 river within 3 hrs driving distance of GTA that are not impacted by rainfall. The rest of the rivers require rain to bring in good # of fish. After a rain, there is a window of opportunity for each river. This could be 1 day after a rain, 2 days after, 3 days after 4 days after, 5 days after and is is different for each river. For example, to go to Bronte in the river and expecting to catch fish this coming Saturday is futile because it hasn't rained for over 10 days.
1 day after a rain I know which rivers to go to. 2 days after a rain I know which rivers to go to. etc. etc. No rain for 20 days, I know which rivers to go to. The more rivers you know and how long they take to get "green" the better you odds are of being at the right river at the right time. You want to be on the river when there are lots of fish in there. That the first part. NO matter how good you are at hooking fish, you won't hook any if the fish aren't there.
The second part is being good at getting fish to bite.